1. Field of the Invention
The disclosures herein relate to an exhaust system and an exhaust system insulator for an internal-combustion engine.
2. Description of the Related Art
An insulator is typically attached to an exhaust system such as an exhaust manifold or pipe of an internal-combustion engine for the purpose of preventing heat radiation and noise.
Patent Document 1 discloses an insulator that is made by assembling a metallic cover member, a mat member comprised of inorganic fiber, and an inorganic heat-resistant cloth member into an integrated structure. The mat member is attached to the inner surface of the cover member, and the cloth member is attached to the surface of the mat member. Tips of four arms of a cross-shaped washer prevent the mat member from becoming slack. Specifically, the four arms of the cross-shaped washer are bent inwards, and the washer is inserted into a space that is made by removing a portion of the mat member through a circular hole opened through the cloth member. The central part of the washer is then fixed to the cover member by spot welding.
The insulator of Patent Document 1 attached to an exhaust system of an internal-combustion engine allows an air current to enter the gap between the exhaust system and one of the cloth member and the cross-shaped washer. This results in the temperature of the exhaust system being lowered. Also, heat may be transferred from the exhaust system to the exposed cross-shaped washer situated opposite the exhaust system, thereby lowering the temperature of the exhaust system. As a consequence, the performance of exhaust gas purification may be lowered.
Further, the insulator disclosed in Patent Document 1 is configured such that the mat member is attached to the inner surface of the cover member. Attaching the mat member by use of an adhesive agent or the like gives rise to the problem of insufficient adhesion strength. The mat member may break away from the cover member due to heat or vibration.
[Patent Document 1] Japanese Patent Application Publication No. 9-49426